1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
4 */
5 #ifndef _ASM_POWERPC_BARRIER_H
6 #define _ASM_POWERPC_BARRIER_H
7
8 #include <asm/asm-const.h>
9
10 #ifndef __ASSEMBLY__
11 #include <asm/ppc-opcode.h>
12 #endif
13
14 /*
15 * Memory barrier.
16 * The sync instruction guarantees that all memory accesses initiated
17 * by this processor have been performed (with respect to all other
18 * mechanisms that access memory). The eieio instruction is a barrier
19 * providing an ordering (separately) for (a) cacheable stores and (b)
20 * loads and stores to non-cacheable memory (e.g. I/O devices).
21 *
22 * mb() prevents loads and stores being reordered across this point.
23 * rmb() prevents loads being reordered across this point.
24 * wmb() prevents stores being reordered across this point.
25 *
26 * *mb() variants without smp_ prefix must order all types of memory
27 * operations with one another. sync is the only instruction sufficient
28 * to do this.
29 *
30 * For the smp_ barriers, ordering is for cacheable memory operations
31 * only. We have to use the sync instruction for smp_mb(), since lwsync
32 * doesn't order loads with respect to previous stores. Lwsync can be
33 * used for smp_rmb() and smp_wmb().
34 *
35 * However, on CPUs that don't support lwsync, lwsync actually maps to a
36 * heavy-weight sync, so smp_wmb() can be a lighter-weight eieio.
37 */
38 #define __mb() __asm__ __volatile__ ("sync" : : : "memory")
39 #define __rmb() __asm__ __volatile__ ("sync" : : : "memory")
40 #define __wmb() __asm__ __volatile__ ("sync" : : : "memory")
41
42 /* The sub-arch has lwsync */
43 #if defined(CONFIG_PPC64) || defined(CONFIG_PPC_E500MC)
44 # define SMPWMB LWSYNC
45 #elif defined(CONFIG_BOOKE)
46 # define SMPWMB mbar
47 #else
48 # define SMPWMB eieio
49 #endif
50
51 /* clang defines this macro for a builtin, which will not work with runtime patching */
52 #undef __lwsync
53 #define __lwsync() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory")
54 #define __dma_rmb() __lwsync()
55 #define __dma_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory")
56
57 #define __smp_lwsync() __lwsync()
58
59 #define __smp_mb() __mb()
60 #define __smp_rmb() __lwsync()
61 #define __smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory")
62
63 /*
64 * This is a barrier which prevents following instructions from being
65 * started until the value of the argument x is known. For example, if
66 * x is a variable loaded from memory, this prevents following
67 * instructions from being executed until the load has been performed.
68 */
69 #define data_barrier(x) \
70 asm volatile("twi 0,%0,0; isync" : : "r" (x) : "memory");
71
72 #define __smp_store_release(p, v) \
73 do { \
74 compiletime_assert_atomic_type(*p); \
75 __smp_lwsync(); \
76 WRITE_ONCE(*p, v); \
77 } while (0)
78
79 #define __smp_load_acquire(p) \
80 ({ \
81 typeof(*p) ___p1 = READ_ONCE(*p); \
82 compiletime_assert_atomic_type(*p); \
83 __smp_lwsync(); \
84 ___p1; \
85 })
86
87 #ifdef CONFIG_PPC_BOOK3S_64
88 #define NOSPEC_BARRIER_SLOT nop
89 #elif defined(CONFIG_PPC_E500)
90 #define NOSPEC_BARRIER_SLOT nop; nop
91 #endif
92
93 #ifdef CONFIG_PPC_BARRIER_NOSPEC
94 /*
95 * Prevent execution of subsequent instructions until preceding branches have
96 * been fully resolved and are no longer executing speculatively.
97 */
98 #define barrier_nospec_asm NOSPEC_BARRIER_FIXUP_SECTION; NOSPEC_BARRIER_SLOT
99
100 // This also acts as a compiler barrier due to the memory clobber.
101 #define barrier_nospec() asm (stringify_in_c(barrier_nospec_asm) ::: "memory")
102
103 #else /* !CONFIG_PPC_BARRIER_NOSPEC */
104 #define barrier_nospec_asm
105 #define barrier_nospec()
106 #endif /* CONFIG_PPC_BARRIER_NOSPEC */
107
108 /*
109 * pmem_wmb() ensures that all stores for which the modification
110 * are written to persistent storage by preceding dcbfps/dcbstps
111 * instructions have updated persistent storage before any data
112 * access or data transfer caused by subsequent instructions is
113 * initiated.
114 */
115 #define pmem_wmb() __asm__ __volatile__(PPC_PHWSYNC ::: "memory")
116
117 #include <asm-generic/barrier.h>
118
119 #endif /* _ASM_POWERPC_BARRIER_H */
120
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